Hand trucks are notoriously well known for use in the manual transport of large and heavy packages over short distances. Such devices employ a generally upright load-supporting frame having a lifting blade projecting forwardly from the frame proximate a lower extreme thereof. Behind the lifting blade is a pair of laterally spaced wheels allowing the lifting blade to pass beneath a package to be transported and upon tilting the frame toward the hand truck operator, the package is supported by the combination of lifting blade and frame pivoted over the hand truck wheels.
It has been recognized that an adequate braking system would be a valuable addition to any hand truck assembly. Safety concerns dictate the need for such a system which would enable the operator to restrain a heavily loaded hand truck as it is moved down an inclined ramp to properly guide and balance the load without having to exert excessive physical force. Without adequate and reliable braking, a heavily loaded hand truck can pull the operator forcibly down an incline causing him to lose balance and injure both himself and the load.
Despite the obvious advantages in providing a hand truck with a suitable braking system, most hand trucks currently sold are vended without braking mechanisms of any type.
There have been a number of prior art attempts to provide hand trucks with braking mechanisms. For example, U.S. Pat. No. 3,276,550 teaches the use of a horizontally aligned bar which, when actuated, frictionally rubs against the tire surface. Obviously, a friction bar-type brake of this sort is only marginally adequate for it results in excessive tire wear, is only viable when the rubber tire surface is dry and provides braking action which varies with tire type and tread.
Another approach was suggested in U.S. Pat. No. 3,422,930 wherein a strap-type brake was provided. The strap is composed of a flexible material wrapped around a drum mounted to rotate in unison with the wheel so that the strap may be pulled tightly against the drum to produce braking friction. Again, this approach provides inadequate results. For example, the accumulation of dust and dirt between the strap and drum diminishes the friction producing surface area of the combination. Further, this approach together with the one discussed previously oftentimes results in an uneven braking action between the two wheels resulting in a pulling of the hand cart in a direction diagonal to the intended line of travel of the hand truck which can obviously result in an extremely dangerous condition.
Finally, none of the brake mechanisms taught by the prior art as being applicable to hand truck operation are capable of being conveniently used to retrofit existing non-brakeable hand trucks. As noted, the vast majority of hand trucks are sold without brakes and it was viewed as a prime object in the present invention to provide a kit capable of simply and conveniently modifying non-brakeable hand trucks in order to provide them with a brake assembly far superior to any previously suggested by the prior art. For example, U.S. Pat. No. 3,968,974 discloses an elaborate hydraulically operated disk brake system which cannot be added to an existing hand truck frame without extensive modification. Such modification would unduly add to the cost of such a product discouraging its adoption and use in practice.